Hi Blonde, sorry you find yourself here. You have every right to snap at him. He deceived you for at least 15 years. Talking is good but talk to more people than just your spouse. Remember to take care of yourself. It may not be healthy for you to be around the person that has hurt you. If that is the case, you don't have to take part in this best-friends and happy-family facade.
How noble of him to put off pursuing his new life until the New Year (I assume to live authentically and seek male partners). When that happens, and he meets someone, you may find his #1 priority changes. As far as I'm concerned, he has used you for years and now he wants to paint the scene as him being some sort of good guy ?
I highly suggest you speak to a lawyer to chart your future (and that of your kids). You should also seek a counselor who specializes in trauma response. You don't have to become enemies, you also don't have to be his friend. All you need to do is co-parent. He is not in charge of how the future will be organized. You also have a voice. Make sure it's not dependent on his latest impulses or that you are not held hostage in order to gain what he owes you and his kids. Tackle it one piece at a time.
Wishing you well.